The present invention relates to novel methods and apparatuses for preparing water soluble dry polymers. Water soluble dry polymers are polymers that are typically hygroscopic and are stored in dry conditions. One key advantage of dry polymers is their weight, which makes them inexpensive to store and transport. Dry polymers are commonly prepared from sticky rubber like materials known as “wet gels”. Wet gels are extremely viscous polymers formed from the polymerization of vinyl monomers in water. Currently, converting wet gels into dry polymers is a lengthy and energy intensive process. This process involves a drying step in which the wet gels are cut into small enough pieces that allow for the rapid removal of water by evaporation without overheating. The dried polymer is then ground into a size that is best suited for a re-dissolving in water at a desired speed.
Continuous operation of the cutting, drying, and grinding processes is the most cost effective manner of producing dry polymer. In a continuous operation, a steady supply of wet gel polymer is continuously fed into the drying step and a steady supply of dry polymer is continuously output. Current continuous dry steps make use of continuous polymerization reactions that are belt fed into the drying step. Maintaining quality control in these operations however is difficult because the short residence time of the monomers in a continuous polymerization reactor makes it difficult to maintain both a high molecular weight and 100% solubility of the resulting dry polymer. In addition too much un-reacted residual monomer often remains further contaminating the product. As a result, industry also makes use of less efficient batch processing and feeding of wet gels to preserve reliable dry polymer quality. Thus there remains a need for an improved method of continuously producing dry polymers that does not sacrifice high quality polymer properties.
The art described in this section is not intended to constitute an admission that any patent, publication or other information referred to herein is “prior art” with respect to this invention, unless specifically designated as such. In addition, this section should not be construed to mean that a search has been made or that no other pertinent information as defined in 37 C.F.R. §1.56(a) exists.